Re: [PATCH v5 02/12] crypto: acomp - Define new interfaces for compress/decompress batching.

[Herbert Xu]

On Sun, Feb 23, 2025 at 12:12:47PM +0900, Sergey Senozhatsky wrote:
>
> > > It also seems that there is no common way of reporting dst_but overflow.
> > > Some algos return -ENOSPC immediately, some don't return anything at all,
> > > and deflate does it's own thing - there are these places where they see
> > > they are out of out space but they Z_OK it
> > > 
> > > if (s->pending != 0) {
> > > 	flush_pending(strm);
> > > 	if (strm->avail_out == 0) {
> > > 		/* Since avail_out is 0, deflate will be called again with
> > > 		 * more output space, but possibly with both pending and
> > > 		 * avail_in equal to zero. There won't be anything to do,
> > > 		 * but this is not an error situation so make sure we
> > > 		 * return OK instead of BUF_ERROR at next call of deflate:
> > > 		 */
> > > 		s->last_flush = -1;
> > > 		return Z_OK;
> > > 	}
> > > }
> > 
> > Z_OK is actually an error, see crypto/deflate.c:
> 
> I saw Z_STREAM_END, but deflate states "this is not an error" and
> there are more places like this.

That would be a serious bug in deflate.  Where did you see it
return Z_STREAM_END in case of an overrun or error?

> So it will ENOSPC all errors, not sure how good that is.  We also
> have lz4/lz4hc that return the number of bytes "(((char *)op) - dest)"
> if successful and 0 otherwise.  So any error is 0. dst_buf overrun
> is also 0, impossible to tell the difference, again not sure if we
> can just ENOSPC.

I'm talking about the Crypto API calling convention.  Individual
compression libraries obviously have vastly different calling
conventions.

In the Crypto API, lz4 will return -EINVAL:

	int out_len = LZ4_compress_default(src, dst,
		slen, *dlen, ctx);

	if (!out_len)
		return -EINVAL;

Cheers,
-- 
Email: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
Home Page: http://gondor.apana.org.au/~herbert/
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